The power factor of an AC electrical power system is defined as the ratio of real power flowing to a load to the apparent power. For example, the power factor of an AC electrical power system having sinusoidal current and voltage waveforms is the cosine of the phase angle between the current and voltage waveforms. The power factor of an AC electrical power system having a non-sinusoidal current or voltage waveform consists of several factors, including the displacement factor related to the phase angle, and the distortion factor related to the non-sinusoidal wave shape.
Generally, real power (e.g., watts) can be defined as the power that produces real work, reactive power can be defined as the power required to produce the magnetic fields (e.g., lost power) to enable real work to be done, and apparent power can be defined as the total power required to produce the desired real power. The power factor of an AC electrical power system can vary between 0 and 1, with 1 representing a purely resistive circuit having no reactive power loss. When the power factor of the AC electrical power system is not 1, the current waveform does not follow the voltage waveform, resulting in not only power losses, but also potentially causing harmonics that travel through the AC electrical power system, potentially disrupting other devices.
Accordingly, power factor correction (PFC) circuits can be used to increase the power factor of an AC electrical power system.